Particle therapy systems use an accelerator to generate a particle beam for treating afflictions, such as tumors. In operation, particles are accelerated in orbits inside a cavity in the presence of a magnetic field, and removed from the cavity through an extraction channel. An example of an accelerator that may be used in a particle therapy system is a synchrocyclotron.
In a synchrocyclotron, a plasma column is produced using ionized gas (e.g., hydrogen). An RF voltage is applied to extract particles from the plasma column, and a magnetic field is applied to maintain those particles in spiral orbits as they increase in energy and radius until they reach an extraction region. The RF voltage is swept across a range of frequencies to account for relativistic effects on the particles (e.g., increasing particle mass) when accelerating particles from the plasma column.